Acoustic system



Aug. 23, 1966 F. H. MAGNUS ACOUSTIC SYSTEM 5 Sheets-Sheet l Filed April 13, 1965 INVENTOR F H MAG/V05 Aug. 23, 1966. F. H. MAGNUS 3, ,0 0

ACOUSTIC SYSTEM Filed April 13, 1965 5 Sheets-Sheet 2 I NVEN'TOR.

BY F: H MA /V05 Aug. 23, 1966 F. H. MAGNUS ACOUSTIC SYSTEM 3 Sheets-Sheet 5 Filed April 13, 1965 Ti 3a.

' INVENTOR. E H. MAG/V05 United States Patent 3,268,030 ACOUSTIC SYSTEM Finn H. Magnus, Washington Valley Road, Morristown, NJ. Filed Apr. 13, 1965, Ser. No. 447,825 3 Claims. (Cl. 181-31) This invention relates to audio systems, and more particularly, to stereophonic sound reproducing systems.

Audio systems attempt to re-create live sound with maximum fidelity. One of the characteristics of live sound is that it is spatially distributed at its place of origin. For example, to a listener of a live symphony, it is apparent that the sound of a particular orchestral section, such as the woodwind section, has a different geographic origin than the sound of the string section. This spatial effect is lost along with much of the richness and character rendition when sound is gathered at a single point and transmitted or reproduced \using a single or monaural channel.

To achieve a spatial quality in reproduced sound, it is known to gather live sound at several distinctive positions and transmit or reproduce the sound thus gathered using separate channels and speaker systems. The resulting reproduction of sound is said to be stereophonic.

In connection with conventional stereophonic systems it has been thought that for best results it was necessary widely to space the speaker system. However, in the case of a conventional two-channel system, with two separate speaker systems for example, a listener is aware of the desired stereophonic effect as long as he occupies a rather critical position with respect to those systems, typically about midway between them. The diffic-ulty is that as the listener moves away from the critical listening position towards one of the speaker systems, the channel associated with that system becomes dominant. The sound from the other channel, associated with the more distant system, becomes submerged and the desired stereophonic effect is lost. Thus, with conventional stereophonic systems, the position of the listener with respect to the reproducers is of critical importance. Additionally, this special requirement has necessitated the use of large console cabinets or complex remote speaker system installations.

Accordingly, I have conceived by my invention an effective solution to the problems presented and have actually constructed a successfully operating and commercially desirable stereophonic sound reproducing system based upon that concept.

In essence, my invention employs an acoustic blending chamber with both individual and joint access to the exterior of the chamber for acoustic waves generated by separate speakers mounted within the chamber, the speakers being identified with separate channels. Actual-ly, I take advantage of the fact that vibration of conventional speaker diaphragms transmits sound energy both forwardly and rearwardly. The rearward moving sound of the several speakers is blended in the chamber and emergesin an omnidirectional attitude. These sounds when joined with the sounds transmitted forwardly by the respective speakers, cooperate to produce a rich, high fidelity consonant effect throughout the listening area, eliminating the critical listening position heretofore encountered. .This concept permits me, contrary to the teachings of the art, to mount all of the speakers in relatively close proximity.

In one embodiment of the invention, the bass frequency speakers are mounted on opposite sidewalls of the chambet, with the forwardly propagated acoustic waves generated by each speaker having access to the exterior through an auxiliary or resonance chamber. Mid-range 3,268,030 Patented August 23, 1966 and high-range speakers for each channel are mounted in the front wall which is also provided with one or more apertures for releasing the reverse or rearwardly propagated acoustic energy generated by the rear surfaces of the various speaker diaphragrns. The foregoing arrangement of speakers within the system produces the effect of multiple sources of sound which tend to preserve the stereophonic effect on the listener regardless of his position in the vicinity of the reproducer.

Since some commercially available speakers of the midrange and high-range type are manufactured with the rear of the diaphragm completely shielded, it would serve no purpose to mount these speakers in the front wall as no substantial acoustic energy would pass rearwardly from them into the blending chamber. Therefore, when speakers of this type are encountered, I mount them in the rear surface of the chamber so that the acoustic energy emanating therefrom enters the blending chamber and is mixed with the energy reaching the chamber from the rear surfaces of the bass speakers. The blended sounds pass out into the listening area, again in omnidirectional attitude, along with the bass sounds from the front surfaces of the bass speakers.

There has thus been outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form \the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of the invention. It is important, therefore, that the claims be regarded as including such equivalent construction as do not depart from the spirit and scope of the invention.

A specific embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawings, forming a part of the specification, wherein:

FIG. 1A is a perspective view of a speaker system in accordance with the invention;

FIG. 1B is a rear perspective view partly broken away of the enclosure of FIG. 1A;

FIG. 2A is a front view of a stereophonic console incorporating the enclosure of FIG. 1A;

FIG. 2B is a top view of the stereophonic console of FIG. 2A;

FIG. 2C is a side view, partly broken away, of the stereophonic console of FIG. 2A;

FIG. 3A is a perspective view of another embodiment of the invention; and

FIG. 3B is a cross-sectional view taken along the lines 3B3B of FIG. 3A.

Referring to the drawings, and particularly to FIG. 1A thereof, there is shown a preferred version of the invention comprising an enclosure 9 including a central blending chamber 10, a left-hand chamber 11-1 and a righthand chamber 11-2, as viewed. Mounted in various ports in the front and side walls of the chamber 10 are the speakers of a two-channel stereophonic system. The left: hand wall of the chamber 10 includes a bass frequency speaker 151 of the first channel. This speaker has a frequency response of several hundred cycles and is commonly designated as a woofer. The opposite right-hand wall of the chamber 10 mounts a similar bass frequency speaker 15-2, only partly shown, for the second channel.

The front wall of the chamber 10 includes an aperture 18. speaker 20-1 for the first channel and high-range speak Below the aperture 18 are mounted a mid-range- 3 ers 21-1 and 22-1 for the second channel. The mid range speaker has a frequency of from several hundred to several thousand cycles. The high-range speakers, commonly designated as tweeters have frequency ranges extending above several thousand cycles, and serve to achieve an appropriate high frequency characteristic.

Above the aperture 18 are mounted a mid-range speaker 20-2 for the second channel and high-range speakers 21-2 and 22-2 similar to speakers 20-1, 21-1 and 22-1, but for the first channel. Electrical connections are made to the various speakers in conventional fashion from, for example, a two-channel cross-over network (not shown) or other filtering arrangement of suitable design. The cross-over network is in turn connected to a standard stereophonic amplifier (not shown).

It will also be appreciated that the speakers themselves are of conventional design and are selected so that the over-all frequency response characteristic for each channel is relatively uniform over the desired audio range.

'The relationship of the bass frequency speakers 15-1 and 15-2 to each other is shown in greater detail in FIG. 1B, which is a rear perspective view partly broken away and looking towards the front of the enclosures shown in FIG. 1A. The speakers 15-1 and 15-2 are mounted in back-to-back configuration in ports in opposite walls of the chamber 10. Acoustic energy produced by the diaphragm of the bass frequency speaker 15-1 for the first channel is forwardly propagated to the exterior of the enclosure through the auxiliary chamber 11-1 which is open at its far end. Simultaneously, forward propagation of bass frequency acoustic energy takes place from the second speaker 15-1 through the second auxiliary chamber 11-2. The presence of the auxiliary chambers 11-1 and 11-2 adds to the resonance of the sound emitted by these bass frequency speakers 15-1 and 15-2.

In addition, because of the way in which the bass frequency speakers 15-1 and 15-2 are mounted in the center chamber 10, the rearward propagation from their diaphragms is subjected to a mixing effect, producing a resulting acoustic effect which emerges through the frontal aperture 18.

Without subscribing to any particular theory as to how the speakers of the illustrated acoustical enclosure produce a non-critical effect, one possible explanation is that the mixing effect, coupled with the ordinary forward propagation from the speakers, disburses sound in such a way that the effect is achieved wherever the listener is positioned within the listening range of the enclosures; and in addition, there is also a mixing effect for the sounds generated by the mid-range and the high-range speakers of the two channels, and propagated through the aperture 18. Moreover, tests of a working model of the invention have shown that the distance of operation of the two bass speakers 15-1 and 15-2 is not critical, neither fidelity nor detail are affected by variations in volume. In a typical example, the enclosure 9 may be of the order of 38 to 50 inches in length and preferably about 44 inches; and may be about 14 to 20 inches square in cross section, and preferably about 16 inches. The chamber is approximately 17 inches long in a 44 inch long enclosure. In the embodiment described, I have used inch bass frequency speakers, 3 inch by 6 inch mid-range and 3 inch high range speakers with excellent results. Additionally, while the aperture 18 is shown as being somewhat shorter than the length of the chamber 10, it may well extend the full 17 inches thereof and is preferably about 4 inches in height.

The enclosure of FIG. 1A is readily included in an over-all stereophonic system, as demonstrated in FIG. ZA showing the front view of a cabinet 30 for the enclosure. The cabinet 30'incorporates the chambers 10, 11-1 and 11-2, an amplifier 31 and a record player 32. Both the amplifier and the record player are of conventional design, the amplifier having electrical outputs which are applied in standard fashion to the various speakers. For

additional auditory effect, the front-sides of the auxiliary chambers 11-1 and 11-2 may include apertures 35-1 and 35-2 which are about 4 inches high and 8 inches long and are shown covered by grille cloth. A top view of the cabinet 30 is presented in FIG. 2B. At the back of the cabinet 30 is mounted a rack 37 which can be used for the storage of records. The rack 37 is also shown in the left-side view of the cabinet 30 presented in FIG. 20.

Referring now to FIGS. 3A and 3B, there is shown an embodiment of my invention which has particular application with mid-range and high-range speakers which are manufactured with the rear surfaces of the diaphragms shielded by the speaker frame which is usually formed of metal. Since no sound energy of any consequence is emitted rearwardly by these speakers, there is no point in mounting them as in FIGS. 1A and 1B. Thus, I provide an enclosure 40 having a left-hand chamber 41-1 and a right-hand chamber 41-2, as viewed, together with a central blending chamber 42 therebetween. The chambers 41-1 and 41-2 are fully open at their remote ends, as shown, and are provided with access openings 44-1 and 44-2 in the respective front walls.

The partitions 45-1 and 45-2 that serve to separate the blending chamber 42 from the end or resonance chambers 41-1 and 41-2 serve to mount the bass speakers or woofers 46 as in the embodiment illustrated in FIGS. 1A to 2B, and are further equipped with openings 47-1 and 47-2 providing communication between the chamber 42 and the respective adjacent resonance chambers.

In this embodiment, the mid-range and high-range speakers 49 are mounted in the rear or the chamber 42 to direct the acoustic energy into the chamber. A series of slots 50 provides access from the chamber in a forward direction to the listening area.

It will be seen that sound from the speakers 49 passes through the blending chamber 42 and out through openings 50 to the listening area. However, within the blending chamber, these sounds are mixed with and enriched by the sound waves emanating rearwardly from the woofer diaphragms. Meanwhile, the blended energy also enters the resonance chambers 41-1 and 42-2 through the openings 47-1 and 47-2 provided in partitions 45-1 and 45-2 where it is further enhanced by the forwardly propagated sound from the woofers. The sound reaches the listening area from the resonance chambers by passing through the open remote ends, as well as forwardly through the access openings 44-1 and 44-2.

I have found that by this embodiment, the maximum use is made of mid-range and high-range speakers of a type which have rearwardly shielded diaphragms to obtain a rich, consonant effect in a listening area without limitation to a critical point or zone therein. the case of the embodiment described in FIGS. 1A to 2B, the stereophonic aspect of the system is maintained by utilizing two channels, the several speakers of which are separated laterally. The dimensions of the various parts and openings shown in FIGS. 3A and 3B may be similar to those set forth in connection with the first embodiment described, and the openings 47-1 and 47-2 are about 12 inches long and l to 2 inches high.

It will be appreciated of course that the enclosures 9 and 40 may be installed in a console or cabinet, as desired, or that they may be constructed as an integral part of the console.

From the foregoing description it will be seen that I contribute a stereophonic system for reproducing sound with a high fidelity effect which eliminates the critical listening position as well as the necessity of relatively Widely spaced speakers and the resulting large consoles or wiring arrangements. At the same time, my system provides rich listening satisfaction for even the most critical listener, with full audio detail without regard to volume magnitude.

As in- I claim:

1. In an audio system of the class described, an enclosure partitioned into a central blending chamber and open ended resonance chambers, first and second sound propagating systems each comprising a plurality of speakers, one speaker of each system being mounted in the partitions to direct its forwardly propagated acoustic energy into one respective resonance chamber and thence to a listening area and its rearwardly directed energy into said blending chamber, the remaining-speakers of each system mounted to-direct their forwardly propagated energy directly into the listening area and their rear- Wardly directed energy into said blending chamber, and means defining an access opening permitting the energy in said blending chamber to pass to the listening area.

2. In an audio system of the class described, an enclosure, means partitioning said enclosure into a central blending chamber and open ended resonance chambers positioned at opposite ends of said blending chamber, first and second sound propagating systems, each comprising a plurality of speakers, one speaker of each system being positioned in axially aligned back to back spaced relationship to direct its forwardly propagated acoustic energy into one respective resonance chamber and its rearwardly directed energy into said blending chamber, means defining access openings between said resonance chambers and said blending chamber, the remaining speakers being mounted to direct their forwardly propagated energy directly into saidblending chamber, and means d fining an access opening in said blending chamber whereby energy is communicated to the listening area.

3. In an audio system of the class described, an enclosure, means partitioning said enclosure into a central blending chamber and laterally open ended resonance chambers positioned at opposite ends of said blending chamber, means defining access openings in the front of each of said resonance chambers, first and second sound propagating systems, said systems each comprising a plurality of speakers of lower and upper frequency ranges, the lower range speakers being mounted in axially aligned back to back spaced relationship relatively to one another in the partitioning means and directing their forwardly propagated acoustic energy into a resonance chamber and their rearwardly propagated acoustic energy into said blending chamber, means defining an access opening between said resonance chambers and said blending chamber, the upper range speakers of each system being laterally spaced and position-ed in the rear wall of said blending chamber and adapted to direct their forwardly propagated acoustic energy directly into said blending chamber, and means defining an access opening in the front of said blending chamber'whereby energy is communicated to the listening area.

References Cited by the Examiner UNITED STATES PATENTS 2,145,318 1/1939 Schenk et a1.

2,174,128 9/1939 Jyrch 181-31 3,026,957 3/1962 Gladstone 1813 1 3,074,503 1/1963 Cool 181-31 3,113,633 10/1963 Eberhardt et al. 181-31 FOREIGN PATENTS 1,075,666 2/ 1960 Germany.

932,738 7/ 1963 Great Britain.

RICHARD B. WILKINSON, Primary Examiner, LEO SMILOW, Examiner.

S. J. TOMSKY, Assistant Examiner. 

1. IN AN AUDIO SYSTEM OF THE CLASS DESCRIBED, AN ENCLOSURE PARTITIONED INTO A CENTRAL BLENDING CHAMBER AND OPEN ENDED RESONANCE CHAMBERS, FIRST AND SECOND SOUND PROPAGATING SYSTEMS EACH COMPRISING A PLURALITY OF SPEAKERS, ONE SPEAKER OF EACH SYSTEM BEING MOUNTED IN THE PARTITIONS TO DIRECT ITS FORWARDLY PROPAGATED ACOUSTIC ENERGY INTO ONE RESPECTIVE RESONANCE CHAMBER AND THENCE TO A LISTENING AREA AND ITS REARWARDLY DIRECTED ENERGY INTO SAID BLENDING CHAMBER, THE REMAINING SPEAKERS OF EACH SYSTEM MOUNTED TO DIRECT THEIR FORWARDLY PROPAGATED ENERGY DIRECTLY INTO THE LISTENING AREA AND THEIR REARWARDLY DIRECTED ENERGY INTO SAID BLENDING CHAMBER, AND MEANS DEFINING AN ACCESS OPENING PERMITTING THE ENERGY IN SAID BLENDING CHAMBER TO PASS TO THE LISTENING AREA. 